Re: [6.2 regression][bisected]discard storm on idle since v6.1-rc8-59-g63a7cb130718 discard=async

Christoph Hellwig
2023-04-04T16:04:13Z

On Tue, Apr 04, 2023 at 12:49:40PM +0200, Linux regression tracking (Thorsten Leemhuis) wrote:
> >> And that jut NVMe, the still shipping SATA SSDs are another different
> >> story. Not helped by the fact that we don't even support ranged
> >> discards for them in Linux.
>
> Thx for your comments Christoph. Quick question, just to be sure I
> understand things properly:
>
> I assume on some of those problematic devices these discard storms will
> lead to a performance regression?

Probably.

> I also heard people saying these discard storms might reduce the life
> time of some devices - is that true?

Also very much possible. There are various SSDs that treat a discard
as a write zeroes and always return zeroes from all discarded blocks.
If the discards are smaller than or not aligned to the internal erase
(super)blocks, this will actually cause additional writes.

> If the answer to at least one of these is "yes" I'd say we it might be
> best to revert 63a7cb130718 for now.

I don't think enabling it is a very a smart idea for most consumer
devices.